There are multiple different studies that often cause conflict in this particular area. The DCCT long term trial unequivocally demonstrated that there is an exponential relationship between increased risk of complications and Hba1C level in Type 1 diabetes, in that once you get to around 6.5%, for every percentage point above that you go, you multiply the risk of complications relative to a non-diabetic (as per the graph below).
The reference to studies being ended early refers to the ACCORD study that ended early due to unexpected higher levels of mortality in those treated intensively. It should be made very clear that this was a study primarily looking at
CVD amongst
Type 2s and as the Jenny Ruhl article states, used a drug in the intensive arm (primarily nearly 92% were taking Avandia, which is Rosiglitazone) which is no longer given to Type 2s due to the risk of heart attacks it induces.
It is considered so dangerous that is was withdrawn from most global markets in 2010.
So in answer to both
@fletchweb and
@Taps18456 the studies that suggested that lowering Hba1C is dangerous for Type 2s has been massively discredited doe to the methods used, and aiming to get your Hba1C below 6.5% is very much the best thing to aim at, as it significantly reduces the risks of complications, and therefore death.